In certain machines, it may be necessary to adjust a machine component, which is rotatably supported by a shaft in a housing, by a certain amount in the axial direction. For example, it may be necessary to adjust a front or end side of the machine component relative to a housing wall so as to maintain a certain axial clearance therebetween during operation.
In rotary screw-type machines, e.g., in rotary screw compressors, the size of the axial clearance between the screw and the housing affects the sealing and thus the efficiency of the compressor machine. Therefore, it is desirable, especially in these cases, to achieve a gap as small as possible, e.g., which is close to zero. However, there should never be any abrasive contact between rotating and stationary machine components.
Generally speaking, relatively-rigid roller bearing assemblies are utilized for setting relatively small axial clearances, and a defined axial gap is set during the installation of the roller bearing assembly, e.g., by placing spacer rings underneath or by displacing adjusting threads on the shaft. However, it is disadvantageous that the adjustment during the assembly is manually complex.
In addition, influences that affect the axial gap width during the operation of the machine, such as thermal expansions of machine components, may not be addressed. Therefore, while performing the manual assembly adjustment using spacers or adjusting threads, it is necessary to consider, already during the assembly step, the amount that the gap width may change during operation due to temperature changes. Generally speaking, an undesirably large clearance must often be accepted in order to avoid the risk of having a relatively small gap decrease during operation to the point that the rotating machine component abrasively contacts a stationary component, e.g., due to differing thermal coefficients of expansions of the rotating and stationary components when the machine subsequently heats up.
DE 298 05 351 U1 and its English-language counterpart EP 0 867 628 A2 describes a bearing assembly for a rotatable shaft that supports a means for performing work during rotation of the shaft. The shaft is supported radially by at least one radial bearing that permits movement of the shaft in the axial direction and has a means for supporting the shaft in the axial direction. The means supporting the shaft in the axial direction is an element fixedly attached to the shaft for rotation therewith. This element is arranged so as to be influenced by electromagnetic forces emanating from a stationary position under influence of a control device acting upon sensor means. The instantaneous axial position of the shaft is detectable by the sensor means for precise axial positioning of the shaft and continuous axial adjustment to effect any position changes required for optimizing the work performed by the means supported by the shaft.